A variety of electronic articles and devices utilize modified surfaces that have nanoparticle layers or nano-scale elements thereon. These articles and devices are made through deposition and patterning of nanoparticles on suitable substrates. These are typically deposited from a liquid or a vapor phase.
Laser-induced thermal transfer processes typically use a donor element, including a layer of material to be transferred, referred to herein as a transfer layer, and a receiver element, including a surface for receiving the transferred material. Either the substrate of the donor element or the receiver element is transparent, or both are transparent. The donor element and receiver element are brought into close proximity or into contact with each other and selectively exposed to laser radiation, usually by an infrared laser. Heat is generated in the exposed portions of the transfer layer, causing the transfer of those portions of the transfer layer onto the surface of the receiver element. If the material of the transfer layer does not absorb the incoming laser radiation, the donor element should include a heating layer, also known as a light-to-heat conversion (LTHC) layer or a transfer-assist layer, in addition to the transfer layer.
In a typical laser-induced digital thermal transfer process the exposure takes place only in a small, selected region of the assembly at a time, so that transfer of material from the donor element to the receiver element can be built up one region at a time. The region may be a pixel, some portion of a pixel or a number of pixels. Computer control facilitates the transfer at high speed and high resolution. Alternatively, in an analog process, the entire assembly is irradiated and a mask is used to selectively expose desired portions of the thermally imagable layer.
U.S. Pat. No. 6,521,324 discloses articles formed by thermal transfer of a microstructured layer having surface-defining microstructured features, as well as the thermal transfer elements and methods for making the articles. The details of the vapor deposition and annealing used in the '324 patent are disclosed further in U.S. Pat. No. 5,726,524.
WO 2005/004205 discloses a method of forming a pattern of filled dielectric material on a substrate by a thermal transfer process comprising exposing to heat a thermally imagable donor element comprising a substrate and a transfer layer of dielectric material.
There is a need for a process that enables single-step deposition of substantially nanoparticle layers onto a substrate for electronic and optical applications. For instance, there is a need for high k printable dielectrics, wherein the dielectric particles make up the substantial wt % of the printable layer. Further, there is a need for a printing process that is dry and therefore does not involve solvent incompatibility issues.